Evaluation of a bioassay method for serum amikacin concentrations

Area of Science:

• Clinical Chemistry
• Microbiology
• Pharmacology

Background:

• Accurate measurement of amikacin serum concentrations is crucial for effective therapeutic drug monitoring.
• Existing methods like radioimmunoassay (RIA) can be complex and require specialized equipment.
• Development of alternative, reliable bioassay methods is essential for clinical laboratories.

Purpose of the Study:

• To evaluate the performance of a new bioassay system for amikacin quantification.
• To compare the accuracy and precision of the bioassay against a standard radioimmunoassay (RIA) method.
• To assess the bioassay's suitability for routine clinical use in determining amikacin levels.

Main Methods:

• A bioassay system involving patient serum, seeded agar with Enterobacter, and incubation was utilized.
• Zones of inhibition were measured after incubation to determine amikacin concentration via a standard curve.
• Serum samples with known amikacin concentrations (8 and 20 µg/mL) were tested in replicates, and compared with RIA.

Main Results:

• The bioassay exhibited lower coefficients of variation (CVs) for within-run, day-to-day, and overall assays compared to RIA for both low and high amikacin concentrations.
• Within-run CVs for the bioassay ranged from 4.7-7.2% (low) and 5.2-6.9% (high), generally lower than RIA.
• A high correlation coefficient of 94% was observed between the bioassay and RIA methods for patient sera.

Conclusions:

• The bioassay system provides a precise and accurate method for quantifying amikacin in patient serum.
• Its performance characteristics suggest it is a viable alternative to RIA for clinical laboratories.
• This bioassay can aid in optimizing amikacin therapy through reliable drug level monitoring.